Saturday, 3 December 2011

Case
I have duplicate records in my source which I want to redirect to a separate destination in my data flow task. Most solutions like the Aggregate Transformation or the Sort Transformation with "Remove rows with duplicate sort values" selected, will remove the records instead of redirecting them.

Example: If there are three identical records (two columns), then two of them should be redirected as duplicate so that I can capture them in an error destination.

Solution
This solution uses a TSQL order by or a SSIS sort in combination with a Script Component to detect and redirect all duplicate records.

If your source is a SQL Server table you could probably come up with a fancy TSQL deduplication script to do the same in less processing time, but this solution is easy and also works for other kind of sources. Even if for example you only want to compare two out of five columns.

1) Source and Sort
Add your source to the Data Flow Task. You need to sort on the columns you want to use for deduplication. If your source is a database table, then you should add a GROUP BY clause to the query else you should add a SORT Transformation right after your source.

3) Edit Script Component: Input Columns
Edit the Script Component and go to the Input Columns tab and select all the columns you want to use for deduplication as ReadOnly (the same fields as you used for sorting).

Select columns.Type doesn't matter.

4) Edit Script Components: Inputs and Outputs, Edit Output
Go to the Inputs and Outputs tab and change the name of the Output port from "Output 0" to "Unique". Also change the ExclusionGroup to 1.

Rename default output port

5) Edit Script Components: Inputs and Outputs, New output
Add a new Output and give it the name Duplicate and change the ExlusionGroup to 1. To connect this new output port to the input port, change the SynchronousInputID property and select the input port.

New Output port

6) The Script
Edit the Script and copy the following code. This script uses reflection to get all selected columns so that you don't have to change the script if you change the input columns. But read the coding comments.

// C# code
// This script automaticly compares the selected columns, but there is one 'bug':
// You have to edit and close this script again if you change input columns.
using System;
using System.Data;
using System.Reflection; // Added
using System.Text; // Added
using Microsoft.SqlServer.Dts.Pipeline.Wrapper;
using Microsoft.SqlServer.Dts.Runtime.Wrapper;
[Microsoft.SqlServer.Dts.Pipeline.SSISScriptComponentEntryPointAttribute]
public class ScriptMain : UserComponent
{
// Create a variable to store the concatenated values for the previous row
string previousRow = "";
public override void Input0_ProcessInputRow(Input0Buffer Row)
{
// Create a variable to store the concatenated values of current row
StringBuilder currentRow = new StringBuilder();
foreach (PropertyInfo p in Row.GetType().GetProperties())
{
// We can't use the _IsNull columns, so ignore them. Also ignore the new output column
if ((p.Name.ToLower().EndsWith("_IsNull") == false) && (p.Name.Equals("Duplicate") == false))
{
try
{
// Concatenate value as string to variable
currentRow.Append(p.GetValue(Row, null).ToString() + "|");
}
catch (ArgumentException)
{
// If the value is NULL (empty) then you can't get the value of it
currentRow.Append("NULL|");
}
catch (Exception ex)
{
// Raise error because something unexpected went wrong
bool pbCancel = false;
this.ComponentMetaData.FireError(0, "MarkDuplicates", p.Name + ": " + ex.Message, string.Empty, 0, out pbCancel);
}
}
}
// Check if the current row and previous row are the same
if (currentRow.ToString().Equals(previousRow))
{
// Redirect to duplicate output
Row.DirectRowToDuplicate();
}
else
{
// Redirect to unique output
Row.DirectRowToUnique();
}
// Fill previous row with current value for next check
previousRow = currentRow.ToString();
}
}

or VB.Net

' VB.Net code
' This script automaticly compares the selected columns, but there is one 'bug':
' You have to edit and close this script again if you change input columns.
Imports System
Imports System.Data
Imports System.Math
Imports System.Reflection ' Added
Imports System.Text ' Added
Imports Microsoft.SqlServer.Dts.Pipeline.Wrapper
Imports Microsoft.SqlServer.Dts.Runtime.Wrapper
<Microsoft.SqlServer.Dts.Pipeline.SSISScriptComponentEntryPointAttribute> _
<CLSCompliant(False)> _
Public Class ScriptMain
Inherits UserComponent
' Create a variable to store the concatenated values for the previous row
Dim previousRow As String = ""
Public Overrides Sub Input0_ProcessInputRow(ByVal Row As Input0Buffer)
' Create a variable to store the concatenated values of current row
Dim currentRow As StringBuilder = New StringBuilder()
Dim p As PropertyInfo
For Each p In Row.GetType().GetProperties()
' We can't use the _IsNull columns, so ignore them. Also ignore the new output column
If ((p.Name.ToLower().EndsWith("_IsNull") = False) And (p.Name.Equals("Duplicate") = False)) Then
Try
' Concatenate value as string to variable
currentRow.Append(p.GetValue(Row, Nothing).ToString() + "|")
Catch ex As ArgumentException
' If the value is NULL (empty) then you can't get the value of it
currentRow.Append("NULL|")
Catch ex As Exception
' Raise error because something unexpected went wrong
Dim pbCancel As Boolean
Me.ComponentMetaData.FireError(0, "MarkDuplicates", p.Name + ": " + ex.Message, String.Empty, 0, pbCancel)
End Try
End If
Next
' Check if the current row and previous row are the same
If (currentRow.ToString().Equals(previousRow)) Then
' Redirect to duplicate output
Row.DirectRowToDuplicate()
Else
' Redirect to unique output
Row.DirectRowToUnique()
End If
' Fill previous row with current value for next check
previousRow = currentRow.ToString()
End Sub
End Class

6) Destinations
Add two destinations and connect the Data Flow Paths to the destinations. When connecting you will have to select the output port.

Choose right output

7) Testing
I added some dataviewers for testing purposes and selected the first three columns for deduplication.

The Result

All roads lead to Rome, so let me know what your solution is!
Update: here is an other cool solution that doesn't need sorting.